1. Field of the Invention
The present invention relates to a method of and apparatus for inputting machining information to a machine tool numerical controller of the type which enables an operator to input machining information necessary for the machining of workpieces in a conversational mode and which controls the machining of the workpieces in accordance with the machining information so input.
2. Description of the Prior Art
Known numerical controllers for lathes or turning machines have an automatic programming function which enables an operator to input data indicative of machining shapes and the like necessary for the machining of a workpiece, in a conversational mode so as to automatically prepare a numerical control program for the workpiece. Machining operations in the numerically controlled lathes or turning machines involve displacing a tool along two orthogonal axes in a plane including the rotational axis of a work spindle and are therefore relatively simple to control. On the other hand, machining operations in machine tools which are called "machining centers" require the relative movement between a tool and a workpiece along each of three axes each perpendicular to one another. Accordingly, it is difficult or practically impossible to apply such an automatic programming function for lathes or turning machines to numerical controllers for machining centers.
Particularly, when an operator inputs machining position data to a numerical controller in a conversational mode, it must be possible for the operator to easily ascertain whether the input machining position data are correct or not. That is, it must be possible for the operator to confirm the input machining positions on the workpiece by reference to a screen image on a display device and if the input machining positions are not correct, to revise the screen image by inputting new machining position data. However, the known numerical controllers neither have the function to display on a display screen different views of a workpiece whose shape is defined in three dimensions, nor have the function to display on the display screen any views wherein the machining position is defined in three dimensions. Accordingly, in the known numerical controllers, it is impossible for an operator to ascertain whether a machining shape defined by figures of a solid or a body is correct or not.
Further, the prior art numerical controllers are designed to display the shape of any blank workpiece by a profile taken along the rotational axis of the blank workpiece, but not designed to accurately display the shape of any blank workpiece which has a partial protrusion or cavernous bore. Accordingly, when the shape of a blank workpiece having a partial protrusion or cavernous bore is input to the known numerical controller, the input shape of such a blank workpiece is displayed quite different from the actual shape thereof, thereby resultlng in that machining positions and shapes on the blank workpiece are very difficult for the operator to confirm.